449 



A second illustration of Protemnodon Antceus is afforded by a part of a right mandi- 

 bular ramus with the four two-lobed molars and the socket of the premolar. It is from 

 an older individual than the type-specimen ; d 4 and m 1 are more worn ; m 2 shows a 

 speck of dentine on each lobe where the fore and mid links rise to terminate on the 

 transverse ridges ; m 3 shows the hinder slope of wear on the summits of both lobes ; it 

 is devoid of postbasal ridge. The extent of the series preserved is 2 inches 3 lines. The 

 socket of p 3 indicates the same size of that tooth as in the type jaw. The characters 

 of the bone are closely repeated. But for the difference of degree of wear of the 

 grinders, and a slight superiority in the older specimen of vertical extent of the ramus, 

 they seemed at first glance to form parts of the same mandible. 



As far as dental characters are shown I am led to refer both the subject of Plate CX. 

 figs. 6 & 9, and that of Plate LXXXVIII. fig. 18, to Protemnodon Antceus. The degree 

 of superiority of size of the mandible, with, perhaps, that of the procumbent incisor, in 

 the latter, may be within the limits of sexual distinction. 



The latter specimen is a portion of a right mandibular ramus with the entire symphysis 

 and socket of the incisor. Like the type-specimen it shows, as compared with Pro- 

 temnodon Mimas, relatively smaller molars and a relatively larger premolar. The depth 

 of the ramus at m' is 1 inch 7 lines, as in the specimen regarded as of an old male of 

 Protemnodon Mimas (Plate LXXX VI. figs. 1-3) ; but the fore-and-aft length of d * in 

 Protemnodon Antceus is 5 lines instead of 6 lines ; and that of m 1 is 6 lines instead of 

 7 lines ; the breadth of the molars is also less, in the present jaw, than in Protemnodon 

 Mimas. There is thus 2 lines difference in the fore-and-aft extent of the two anterior 

 bilophodont teeth in Protemnodon Antceus and in Protemnodon Mimas, together with 

 the absence of the postbasal ridge (compare, e. g., Plate CX. figs, 4, 6, 7, with Plate 

 LXXXVI. figs. 1-5). 



Protemnodon Anak, on the other hand (Plate LXXXV. figs. 7-9), is in a greater 

 degree too small, and more especially so in relation to the size of the jaw-bone. 



In Protemnodon Antceus the extent of the three molars (d *, m 1, m 2) is 1 inch 8 lines 

 (43 millims.) ; from the back of the socket of m 2 to the front of that of p 3 is 2 inches 

 7 lines (58 millims.). The prebasal ridge (/*), with the fore link, seems to have been 

 rather less developed than in Protemnodon Mimas ; the premolar had a greater relative 

 length of crown. 



§ 19. Pachysiagon* Ferragus, Ovv. — The characters of certain fossils from the fresh- 

 water beds of the Queensland province, showing the hindmost mandibular molars of the 

 general type of those of the Macropus Titan, but with modifications indicative of specific 

 difference, will be better understood if I premise figures and descriptions of the corre- 

 sponding molars at a similar stage of wear and age, which are plainly referable to 

 Macropus Titan. 



In the subjects of figs. 12 & 13, Plate LXXXIII., the last mandibular molar had 

 but recently come into use ; the edges of the two main lobes showed the backwardly 



* From Tali's, thick ; aiaywv, jaw-bone. 



